Few airplanes in the history of flight have become as legendary as Lockheed’s series of Blackbirds. Designed by the iconic Skunk Works, this family of aircraft took speed, altitude, and technology to the very limits. The most famous planes of the series are the YF-12 interceptor and the SR-71 reconnaissance aircraft, both of which had been vital tools for the pioneers of high-speed, high-altitude flight.
The Lockheed YF-12 was an American prototype interceptor, a twin-seat version of the secretive single-seat Lockheed A-12 reconnaissance aircraft. This aircraft held speed and altitude world records of over 2,000 mph and over 80,000 ft, records later surpassed by its successor, the SR-71. The YF-12 remains the world’s largest manned interceptor to date.
By the late 1950s, the United States Air Force (USAF) needed to find an interceptor aircraft to replace the F-106 Delta Dart. The winning design of the competition was the North American XF-108 Rapier, developed under the umbrella of the Long Range Interceptor Experimental (LRI-X) program. The project was closed out in September 1959, though. It is during this period that Lockheed was developing their A-12 for the CIA under the codename Oxcart. An affiliated version, the AF-12, was proposed by Skunk Works’ Johnson and ordered by the USAF in mid-1960. The USAF designated these planes YF-12A interceptors.
The structural modifications in the A-12 for the YF-12A design were substantial. The design of the nose was altered in geometry to accommodate the Hughes AN/ASG-18 fire-control radar. A second cockpit was also added to the design, for another crew member to run the radar and missile system. The new changes directed the use of ventral fins beneath the fuselage and engine nacelles to maintain stability. The bays of the bays, which were originally in place for the reconnaissance equipment, were reconfigured to carry Hughes AIM-47 Falcon missiles.
The first YF-12A flew on 7 August 1963. President Lyndon B. Johnson publicly announced the existence of the aircraft on 24 February 1964, in part to obscure the still-secret A-12 program. On May 1, 1965, the YF-12A established world speed and altitude records of 2,070.101 mph and 80,257.86 ft. The program was cancelled shortly thereafter because the funding ceased for the production version, the F-12B, when priorities of the U.S. defense shifted into space-based retaliatory capability with the development of the Manned Orbiting Laboratory, or MOL.
The YF-12s continued to serve as experimental aircraft for the USAF and NASA. NASA conducted studies on engine inlet performance, boundary layer noise, heat transfer under high-Mach conditions, and altitude hold at speeds greater than that of sound. The YF-12 program provided valuable data that contributed to the development of future supersonic aircraft.
The SR-71 was developed from the YF-12 and became an aircraft that could cruise at Mach 3+ speeds at well over 85,000 feet, ultimately becoming the world’s fastest high-flying plane. It has been used in many types of high-speed and high-altitude research by NASA over the years. Constructions in titanium allowed the SR-71 to tolerate high heat that a flying body produces when sustained at Mach 3.
The Dryden Flight Research Center of NASA also flew the three SR-71 aircraft for multiple experiments carried out during the 1990s. Some of these were a Sonic Boom Mitigation Study, which sought to find ways to weaken the shock waves that create the sonic boom heard and felt on the ground; the Linear Aerospike Rocket Engine (LASRE); and experiments in the observation of celestial bodies using an ultraviolet video camera.
From the YF-12 interceptor to the SR-71 reconnaissance aircraft, the legacy of the Blackbird series is one that represents ingenuity and vision—such was the Lockheed Skunk Works. Not only were new records set with these aircraft, but they also paved the way for improvements on aeronautical research and technology in the future.